Method of apparatus for cooling high-temperature metal bars

ABSTRACT

A method of countinously cooling high-temperature bars as they are transferred in the direction of their width in groups each consisting of a plurality of bars in close contact side by side with each other on the cooling bed, by turning the bars over thereon so that the sides of the bars are put into close contact with the sides of the adjacent bars at various different positions, such transference and turning-over being alternated for continuous cooling, and an apparatus for said method.

United States Patent [1 1 Harada et al.

[ METHOD OF APPARATUS FOR COOLING HIGH-TEMPERATURE METAL BARS [75] Inventors: Toshio Harada, Kisarazu; Jinichi Akayama, Kitakushu; Masanori Yokozeki, Kisarazu; Toshihiro Ishimura; Shinji Nagano, both of Kimitsu; Hiroshi Wakuda; Kazuhiko Shimomura, both of Kitakyushu; Akira Matsunami, Kimitsu, all of Japan [73] Assignee: Nippon Steel Corporation, Tokyo,

Japan [22] Filed: Feb. 15, 1973 [21] Appl. No.: 332,755

[30] Foreign Application Priority Data May 23, 1972 Japan 47-50884 [52] US. Cl. 72/201, 266/2 R [51] Int. Cl B2lb 43/10 [58] Field of Search 72/201, 252, 364; 266/2 R Dec. 10, 1974 [56] References Cited I UNITED STATES PATENTS 744,874 11/1903 Neeland.... 266/2 1,992,361 2/1935 Diescher 266/2 3,693,954 9/1972 Toperzer et al. 266/2 Primary ExaminerLowell A. Larson Attorney, Agent, or Firm--Wenderoth, Lind & Ponack [5 7 ABSTRACT A method of countinously cooling high-temperature bars as they are transferred in the direction of their width in groups each consisting of a plurality of bars in close contact side by side with each other on the cooling bed, by turning the bars over thereon so. that the sides of the bars are put into close contact with the sides of the adjacent bars at various different posi-' tions, such transference and turning-over being alternated for continuous cooling, and an apparatus for said method.

11 Claims, 11 Drawing Figures PATENTEBBEC 10 I974 SHEET m 3 3.852.989

FIG. 8

6) AT THE PROGRESSING LIMIT BACKWARD M FQRWARD l2 s METHOD OF APPARATUS FOR COOLING HIGH-TEMPERATURE METAL BARS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of and an apparatus for cooling high-temperature metal bars, particularly a method of cooling such bars on the cooling bed while warps are corrected by the bar weight, without producing thermal strain, and particularly a cooling bed equipped with a device for transferring and turning over such bars.

2. Description of the Prior Art There have been hitherto widely known the methods of cooling metal bars (with a round cross section or a multilateral shape or ribs or such so that the element looks like a bar in its entity) on the cooling bed, as they are turned over in one way or another for the correction of warps by utilizing their own weight, as in the case of cooling billets from the rolling temperature to room temperature.

One type of cooling bed used for cooling such bars as mentioned above consists of fixed skids and movable skids and another type bar fixed skids and slant skids. The cooling bed of the former type has each of the fixed skids and movable skids provided with a number of rectangular or round grooves so that a bar will be received in each such groove; and the bars are passed over from a fixed skid to the next movable skid by means of the vertical movement of the movable skids, thus these bars being transferred and turned over at the same time. As for the latter type of the cooling bed, slant skids are provided on the frames which are movable along the fixed skids and dogs; and bars hit the dogs, and slide up the slant skids and then fall onto the fixed skids, while being turned over.

The turning over of bars is caused by rolling through an appropriate angle in the case of round bars or by turning over to different sides in the case of square bars. As long ash is carried out at a high temperature within the temperature range in which plastic deformation may take place owing to the bar weight, it is possible to correct warps by the weight of the bar itself and cool all the sides uniformly by turning the bars over, thus changing the sides in contact with the cooling bed surface from one to another.

In the cases of cooling such high-temperature metal bars conventionally, such bars are placed on the cooling bed one by one spaced at an interval each from the other, in order to have all the sides uniformly contacted by air or cooling water, thus making the cooling speed uniform for all the sides thereof, for the prevention of thermal strain. However, providing such an interval between them requires a greater size of the cooling bed, and a much larger space for the cooling plant, requiring a much larger investment. Also, for cooling hightemperature metal materials conventionally, in one known method air cooling is used at a high temperature of the materials within the temperature range which is high enough to permit rapid cooling, until such temperature drops to such a level that the cooling speed is lowcred; then a switch is made to cooling with water. According to this method, it may be possible to cool the materials to the neighborhood of room temperature in a comparatively short time, without production of thermal strain due to the temperature difference between the surface and the inner part of the materials. However, in the usual case, water cooling is at such rapid pace that the temperature distribution inside the materials tends to become non-uniform, producing thermal strain. Therefore, care must be taken to have all the sides of the materials cooled uniformly. Particularly in the case of water cooling carried out conventionally, the materials are immersed in cooling water; if they are in close contact in the cooling water tank, there will be a great difference in the cooling speed between the side contacting water and the side contacting adjacent pieces, causing a great difference in temperature and producing thermal strain and cracks. Therefore, it becomes necessary to have the materials placed one by one at spaced intervals from each other on the cooling bed, as mentioned above.

In the case of cooling the materials in a water tank, a disadvantage that the best suited type of cooling bed needs be selected according to the size, shape and quality of the materials.

In the case of cooling equipment of the conventional type, the materials are placed on the cooling bed one by one at an interval each from other, therefore, the cooling operations carried out thereby are not efficient; in the case of cooling billets, for example, as a result of the greatly raised rolling capacity of the present rolling mills, billets are rolled out at the rate of3 m/sec; if they are made in a commercial size of 6 meters, the cooling equipment will have to receive one such piece every 2 seconds.

However, it will be very difficult for one cooling bed to receive billets accurately one by one onto the cooling bed at such a rapid rate; therefore, a number of the cooling beds are required-for the conventional type of cooling equipment. In order to avoid the situation as described above, the cooling capacity of the cooling bed should be raised in such way that the materials are placed on the cooling bed in groups each consisting of a plurality'of rods or the like.

Also, according to the cooling bed of the conventional type, the turningangle of the materials depends on the size of the grooves to receive such materials, the slant skids and various other parts of the cooling bed; therefore, in order to handle the predetermined size of the materials, a cooling bed must be selected from this standpoint. For example, in the case of a cooling bed using slant skids, a square bar having a side mm long turns 180, that having a side of 180 mm does not turn, and that having a side of l 15 mm turns a round bar does not turn but slides on the slant skips until it falls therefrom, which may be far from uniform cooling and the correction of warps by its own weight.

Since the usual case is one and the same same rolling mill being used to roll out various sizes and shapes of products, a number of the cooling beds are provided to meet a variety of sizes and shapes of the to-be-cooled materials.

SUMMARY OF THE INVENTION As a solution of the problems with the conventional methods of cooling metal bars, the present invention has as an object to provide a method of cooling hightemperature bars with high cooling efficiency.

Another object of the present invention is to provide a method of rapidly cooling bars from a high temperature to room temperature without producing thermal strain and cracks.

A further object of the present invention is to provide an apparatus for cooling bars by groups each consisting of a plurality of bars.

A further object of the present invention is to provide a cooling apparatus capable of cooling a variety of sizes and shapes of the to-be-cooled materials on one and the same cooling bed.

Other purposes of the present invention will make themselves explicit from the following explanation and the accompanying claims.

In order to achieve the abovementioned objects, the method of cooling high-temperature metal bars according to the present invention has its special characteristics in the steps of placing high-temperature metal bars on the cooling apparatus by groups each consisting of a plurality of rods in close contact side by side each with other, cooling said bars as they are transferred in close contact side by side each with other on the 00010- ing bed, and turning over said bars on the cooling bed so that any side is put into close contact with any side of the adjacent bars, such transference and turningover of said bars being alternated for continuous cooling.

In order to achieve the abovementioned objects, the apparatus for cooling high-temperature metal bars has its special characteristic in the provision of a cooling bed with slant skids effective for turning over such bars, and with dogs for sliding the bars up the slant skids.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a cooling bed as it carries hightemperature metal bars for cooling by the method of the present invention.

FIG. 2 is a graph showing the course of a drop of the surface temperature of high-temperature steel bars as a result of the water cooling by the method of the present invention.

FIG. 3 (a) is a schematic side view showing billet rearrangement and an apparatus therefor according to the invention.

FIG. 3 (b) is a locus diagram of motion of an extractor arm of the apparatus shown in FIG. 3 (a).

FIG. 4 is a schematic plan view of the apparatus shown in FIG. 3 (a).

FIG. 5 is a schematic side view of billets rearranged in comparison with their previous arrangement.

FIG. 6 is a perspective illustration showing part of the cooling bed of the present invention.

FIG. 7 is an enlarged side view of an apparatus for transferring and turning over to-be-cooled materials on the cooling bed shown in FIG. 6.

FIG. 8 is explanatary illustration of the operations of the apparatuses for turning over square materials and round materials.

FIG. 9 is a schematic side view of the apparatus for transferring and turning over, to-be-cooled materials showing another operational embodiment.

FIG. 10 is a schematic side view of the apparatus for transferring and turning over to-be-cooled materials showinga further operational embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT The following is the preferred embodiment of the present invention using billets as to-be-cooled materials:

In reference to FIG. 1, the billets S rolled out from the blooming mill are transported by a roller table 1 to the inlet of a cooling bed 3 which lies at a right angle to the roller table 1; the temperature of the billets is about 900 l,lO0C.

The billets S which have been transported one after one from the blooming mill, are put together into a group-L of 3 to 8 pieces on an arranging table (not shown); and then transported to the roller table in front of the cooling bed 3. The billets S which thus have reached the start of the cooling bed 3, are pushed onto the cooling bed 3 by a pusher 2 which is set adjacent to the roller table 1.

As a member ofa group L, each billet S is side by side with and in close contact with the adjacent billets S, while groups L are at some interval from each other.

Thus, the billets S are transferred in groups from the inlet to the outlet of the cooling bed 3 in the direction of their width for continuous cooling.-

As for the end billets S of any group, one side is exposed to the air, and the other side is in close contact with the adjacent billet S.

Therefore, the first-mentioned sides (facing outside of the group) of such billets get cool and contract faster than the second-mentioned sides facing inside of the group), resulting in warping thereof outwardly. from the group. In order to prevent such thermal deformation,

the billets S are turned side over side by the transferring and turning-over apparatus provided on the cooling bed 3; by such turning-over the billets S the sides of the billets S contacting the top surface of the bed 3 are changed, therefore making it possible to correct warps of the billets S by their own weight.

In order to prevent thermal deformation in the billets S, and also cool them with one cooling bed while transferring them at a high pace, the period of one turningover of the billets S should be within tens of seconds.

The warping starts earlier the higher the temperature to which said billets S are heated and starts later the greater the sizes of said billets S. Thus, the billets S warp more with a lapse of time, so that such warping may become great enough to hinder their turningover on the cooling bed. Therefore, it is desirable to turn over billets S before the start of warping. For example, a billet having a square section respectively of I 15 mm and 185 mm length of side, can be turned over about every 60 seconds and every second, with no warping that is great enough to hinder turning-over of billets. In this embodiment, the interval between turning-over of the billets (hereinafter called the turning-over cycle) is set at 90 seconds maximum, taking the abovementioned situation into consideration.

The cycle of the turning-over of billets should be as short as possible for the prevention of warping, but the shorter the cycle, the greater the number of turningover actions of billets, requiring a much greater length of the cooling bed 3, which is a disadvantage from the standpoint of equipment economy. On the other hand, if the turning-over cycle progresses at a slower pace than billets S are charged onto the cooling bed 3, the capacity of the rolling mill must be held down to meet such cycle. Therefore, the minimum turning-over cycle should be set so as to more than meet the capacity of the rolling mill. In this embodiment, the minimum turning-over cycle is set at 30 seconds, to meet the maximum production capacity of the most modern rolling mill, which is seconds in terms of the time required for one group. Also, in order to reduce the space required for the cooling bed 3, the billets S, as the members of the group L, havethe sides kept in close contact with the sides of the adjacent billets S even after having been turned over.

For the reduction of the space for the cooling bed 3, but taking into consideration the need for the turningover of billets S, the interval between each two groups L should be about 2 or 3 times as long as the greatest width of the to-be-cooled billets S.

As described above, billets S are transferred by groups, and cooled on the cooling bed 3 as they are transferred; such cooling of billets S is achieved as the billets move in the direction of transference with air and water. Air cooling of the billets S starts at the high temperature of about 1,100C (rolling temperature) and is continued to 600C in the high temperature range cooling operation; and water cooling starts at the temperature of 700C and is continued to room temperature in the medium temperature range cooling operation.

In the high temperature range cooling operation, the

billets S are cooled at a comparatively high cooling speed even by air cooling because of the great difference between the surface temperature of the billets S and the ambient air temperature.

Also, in the high temperature range cooling operation, the billets S are still susceptible to plastic deformation by their own weight, so the air-cooling of the billets S, as they are turned over, ensures uniform cooling and will prevent warping due to thermal strain, and

correct even the already produced warping by the weight of the bars to shape them into the right form.

When the billets S have been cooled by air below transformation point A, into the medium temperature range in which plastic deformation will not take place, the cooling operation is switched to forced cooling by water, so as to expedite cooling in the subsequent temperature range, thereby reducing the overall time required for cooling. By the time the water cooling starts, the temperature of the billets has already fallen to a low level, and they will warp only with difficulty, so that it is not always necessary to turn over the billets. As the temperature falls, the time required for cooling per unit of temperature increases; so the time required for cooling below the medium temperature range, is far longer than that required for cooling from above the medium temperature range. Therefore, reduction of the time required for cooling below the medium temperature range results in a substantial reduction of the overall time required for cooling. The time required for cooling is not so greatly different from that where the forced cooling is applied exclusively throughoutthe operations. Moreover, once the right billet form is obtained in the high temperature range, in which the billets are susceptible to plastic deformation, this form can be kept unspoiled throughout the operations. Also, the billets have nearly been annealed in the vicinity of the transformation point A,, as they are slowly cooled there.

As the billets are subjected to forced cooling after the right form has been achieved, and the right form is not obtained by cold working, there is no internal stress carried over which has been produced during the cold working.

According to the present invention, in order to prevent such plastic deformations as warps and distortions,

the cooling of billets is achieved by alternate forced cooling and the recovery of the surface temperature. The range of temperature drop to be achieved during one rapid cooling operation depends on the temperature of the billets. If such range is too great, the billets will deform, therefore, it must be an appropriate range, taking the heat capacity of the billets into account. Thus, the first rapid cooling is within a range in which the billets will not deform.

The range of temperature reduction in one rapid cooling operation may be smaller if the temperature of billets is higher, and larger if such temperature is lower; but, in the case of cooling billets which are of 600 700C, if the range of temperature drop is within 100C, there will be no warping of the billets; if such range is too great, the billets will warp. 1f the temperature before cooling is low, there will be no warping, even if the range of temperature drop is more than 150C.

Water cooling is by sprays from the nozzles 4 arranged above and below the cooling bed 3. The volume of the sprays is so adjusted as to achieve the desired cooling speed.

FIG. 2 shows one example of the curves of the drop of the surface temperature of billets. 1n the drawing, 1 indicates the range of air cooling; and 11 indicates therange of water cooling. The size of the billets is mm X 70 mm X 9,000 mm. As described above, the billets are transferred by groups each consisting of four pieces and are turned over on the cooling bed. The billets of each group are in close contact with the adjacent ones.

Air cooling is continued until the surface temperature of the billets falls to 800 600C, that is, below the transformation point A,; the cooling throughout this period is indicated in FIG. 2 by a for the beginning and b for the finish. The time required for air cooling is 20 40 minutes, during which time the billets are turned about 20 times.

The surface temperature of the billets at the start of the first rapid cooling operation is 650C. The billets are sprayed with jets of cooling water at a flow rate of 3.5-20 llminm onto the top surface and at a flow rate of 20-140 l/rninm onto the bottom surface, for 1 minute in both cases. The cooling throughout this period is indicated in FIG. 2 with b for the beginning and with the note c for the finish. The surface temperature of the billets after cooling is 550C. Then, the billets are.

left for natural cooling for 2 minutes. During the natural cooling, the surface temperature of the billets returns to 570C from the heat latent in the inner part thereof, as shown at c and d. After the rise of temperature in the surface part of the billets, water cooling is made carried out for one minute, and the surface temperature falls to 450C. Then, natural cooling is carried out for 2 minutes so that the surface temperature rises to 470C. This course is shown at d e -f.

Subsequently, a third water cooling operation is carried out for 45 seconds, so as to reduce the surface temperature to 350C; and this is increased to 365C during the natural cooling which follows for 2 minutes. The'fourth water cooling operation continuing for 45 seconds reduces the surface temperature to 230C. This course is shown atfg h i.

and natural cooling, that is, the rise of the surface temperature, prevents such bars from distorting; therefore, the method of the present invention is so efficient as to make the correction of warping unnecessary after cool ing operations.

Also, according to the present invention, water cooling is carried out not by a method using a water tank, but by cooling by stages with sprays. The latter method makes if possible to control cooling conditions (such as cooling speed and cooling time) and transference conditions (such as transference speed and lot size) much more freely than with the former method; therefore, the latter method is applicable to materials of a wider variety in quality, size and shape than the former method. In the latter case, therefore, the cooling bed need not be provided in a number of routes for different varieties of to-be-cooled materials according to the quality, size and shape, and, one cooling route can handle all such varieties of materials.

As shown in FIG. 1, billets S are transferred at a predetermined pace by a plurality of dogs the number of pieces to be handled by each dog 5 is varied according to the size of steel ingot or to-be-cooled materials, so it is not constant in all cases. Moreover, as the pace of the dogs must be such as to meet the maximum width of the materials to be produced from one steel ingot, such materials are transferred in most cases at a rather large interval, as shown in the drawings. However, the billets S cooled in the air-cooling zone I generally have a temperature of less than 700C, and therefore, they are not susceptible to such great warping as when they are at a high temperature, so there is no need of cooling them in the same group arrangement as used in the aircooling zone I. Therefore, by putting the billets into a new group arrangement at the time of switching the aircooling to the water-cooling, it is possible to further raise the operation efficiency of the cooling bed.

As the volume of materials handled by the crane is according to the number of billets handled by the receiving dogs, the crane may not be operated at its full capacity. Also the stockyard at the outlet ofthe cooling bed can have a frame prepared as designed originally, for great convenience in terms of material handling.

FIG. 3 a and FIG. 4 show one example of the lay-out of the apparatus for the practice of the present invention, in which 5 indicates to-be-cooled materials such as billets; 5 indicates dogs, numeral 6 indicates the arm of an extracter for the rearrangement of groups of materials, numeral 7 indicates a pinion engaging with the rack provided on said arm 6 and numeral 8 indicates a roller table connecting a first transferrer' 9 for the transference of materials S before group rearrangement with a second. transferrer 9' for the transference of materials S after group rearrangement.

In the above lay-out, the pieces S which are to be transferred in groups of an appropriate number of pieces by each dog 5, are put together at the position of the frontmost dog 5. As shown in FIG. 3 a, the arm 6 of the extracter is extended to a position below the put-together pieces S by the rotation of the rack 7, and, then, said arm 6 is lifted up by an appropriate type of lift to receive the predetermined number of the pieces thereon, and further, said arm 6 is moved to a position above the roller table 8 and let down, so that the pieces S are placed on the roller table 8 for further transference. The pieces S which have been transferred in the predetermined number, are transferred by a dog (not shown) of the second transferrer 9 to the predetermined position, as they are cooled, and then taken out of the cooling apparatus by the crane. FIG. 3 b shows a locus of the arm 6 of the extractor; its locus which is an irregular quadrilateral represents of one cycle of the extraction work; and the repetition of this cycle makes it possible to transfer the pieces S group by group each consisting of the same number of'pieces and each at a certain interval from the other onto the roller table 8.

Therefore, according to the present invention, as shown in FIG. 5, pieces S which were transferred in groups of various numbers during cooling operations, are rearranged by the group rearrangement equipment (such as the extracter) into groups of the same number of pieces per dog 5, and are transferred to the next step efficiently by the lifting magnetic crane 10, as they are efficiently cooled. For this purpose, it is necessary to have the number (total width) of the pieces received by each dog 5 correspond nearly with the maximum capacity of the crane 10 in terms of width of the to-besuspended object.

As described above, the method of the present invention is effective in raising the operation efficiency of the cooling bed, and makes it possible to utilize the suspending capacity of the crane to a maximum, thereby greatly raising the capacity for cooling metal bars such as billets.

The following is the explanation of the cooling bed equipped with the mechanism for transferring and turning over to-be-cooled pieces, as described above, according to the-present invention.

The cooling bed 3 consists mainly of fixed skids l1 and driving plates 21, as shown in FIG. 6 and FIG. 7.

The fixed skids 11 extend at right angles to the roller table 1, and are fixed at certain intervals from each other.

Knife-shaped, fixed rocking dogs 12, are on the sides of the fixed skids 11 on pins 17 near their center for free rotation. The tip 13 of each of the fixed rocking dogs 12 projects above the top surface of the fixed skids 11. The fixed rocking dogs 12 have their base 16 slightly larger than the tip 13, so when they are left free, they rotate to a position with base 16 pointing downward due to its weight. However, the rotation of the fixed rocking dogs 12 is checked by the contact of the base 16 with stops 18 fixed on the side of the fixed skids 11; the contacting surface 14 of the fixed rocking dogs 12 or the tip 13 is inclined at an angle of nearly 25C to the top surface of the fixed skids 11; and the receiving surface 15 of the tip 13 is perpendicular to the top surface of skids 1l.'

The driving plates 21 are each made up of a pair of parallel plates each extending parallel with the fixed skids 11 and positioned between the fixed skids. The driving plates 21 are placed on a plurality of rollers 35 positioned at intervals along said fixed skids, and are each driven forward bnd backward by a hydraulic cylinder 36 provided at the end of the plates at a rate of 0.05 to 0.4 m/sec.

The top surface of the driving plates 21 is slightly below the top surface of the fixed skids 11, and is provided with slant skids 22 at certain intervals each from other, projecting above the top surface of the fixed skids 11. As viewed from the side, each of the slant skids 22 forms a trapezoid; its rising angle a (the inclined angle of the rising side 23 extending to the rear) is and the declining angle ,8 (the inclined angle of the declining side 25 extending to the front) is 40 50; the height k of the slant skids 22 is about 0.4 to 1 times the height of the to-be-cooled pieces (the length of a side in the case of a square piece; and the diameter in the case of a round piece); and the length 1 of the plain part 24 is about 0.6 to 1 times the length dimension of the pieces in the direction of the length of the skids.

The driving plates 21 are provided with movable rocking dogs 28 beside the slant skids 22 mounted on pins 33 for free rotation. The movable rocking dogs 28 have the same shape and size as the fixed rocking dogs 12 of the abovementioned fixed skids l1, and are also blocked from rotation by the stops 39 fixed on the driving plates 21 so as to stay inclined at 45. The contacting surface 30 of the tip 29 of the movable rocking dogs 28 is inclined at about 45 relative to the top surface of the fixed skids 11; and it nearly perpendicularly crosses the declining side 28 of the slant skids 22. The receiving surface ,31 of the tip 29 is always perpendicular to the top surface of the fixed skids 11.

There will now be described the transferrence and turning-over of billets on the cooling bed having the abovementioned structure; reference being made to the parts of FIG. 8;

As described, billets S are put together in groups each consisting of several pieces, and are transported onto the cooling bed 3, that is, the fixed skids 11. At that time, the driving plates 21 are positioned at the regressing limit (shown at the leftmost side in FIG. 8), and the movable rocking dogs 28 are positioned right after the billets S placed in a group. In this situation the forward movement of the driving plates 21 causes the receiving side 31 of the movable rocking dogs 28 to contact with the side ofthe rear-end billet S, and such movement will be continued, pushing the group of billets S, which, as it moves forward past the fixed rocking dogs, pushes down the fixed rocking dogs 12 on the fixed skids 11.

The driving plates 21 stop at the progressing limit (shown at the rightmost side in FIG. 8). At that time, the billets S have moved forward by one stroke, after which the fixed rocking dogs 12 which have been pushed down, standing up of their own accord to resume the original positions.

Having reached the progressing limit the driving plates 21 start regressing. With the regression of the driving plates 21, the group of billets S as a whole start regressing. The rear-end billet S contacts the receiving side 15 of the fixed rocking dogs 12. At that time, the fixed rocking dogs 12 stop the regression of the billets S, because to the dogs 12 do not rotate in the backward direction due to the stop 18. Even after the billets S stop, the driving plates 21 continue regressing, so that starting with the formost one, the billets S one after another are lifted by the slant skids 22.

As the top 26 of the slant skids 22 move under the billets, the billets S start turning over that top as a center, and start sliding down the declining side 25 of the slant skids 22 at the finish of their turning by about 45 Then the billets S contact with the contacting side 30 of the movable rocking dogs 28, and, while being supported by the movable rocking dogs 28 turning clockwise under the weight of the billets S, the billets S fall down to the falling point 27, where the billets S again turn by 45, resulting in a turn of 90 from the original position.

After all the billets S of the group have turned over, the driving plates 21 reach the regressing limit. At that time, the movable rocking dogs 28 which have been rotated in the forward direction by the billets S sliding down the declining side 25 of the slant skids 22, stand up of their own accord and resume the original position.

Through the repetition of the abovementioned actions of the apparatus, billets S are transferred in groups and turned over for continuous cooling.

On the cooling bed of the present invention, billets S turn over through a limited angle and slide down the slant skids 22 while supported by the movable rocking dogs 28, which makes it possible for billets S of a wide variety in size (for example, of 265 mm for one side) to be turned accurately side over side. Also-as the impact, which may be produced by falling from the slant skids 22 to the fixed skids 11 is alleviated, the billets S are protected from bruises.

Such course of transference and turning-over as described above can be used not only for the air-cooling temperature range I, but also for the water-cooling temperature range II.

The above explanation has been given for operations using square pieces as the to-be-cooled pieces. As 9 shown in FIG. 8, round pieces R rolling down the slant skids 22 are supported by the movable rocking dogs 28, so one turning-over operation is usually 2 to 4 rotations.

According to the present invention, the speed of the driving plates 21 is 0.05 to 0.4 m/sec., and the rising angle of the slant skids 22 is 10 to 20, as described above, in order to prevent the pushup phenomenon (a round piece in a group may be pushed up by the round pieces adjacent thereto) from taking place with a group of round materials sliding up the rising side 23 of the slant skids 22, as being pushed by the fixed rocking dogs 12.

In the abovementioned embodiment, the configuration of the slant skids 22 is a trapezoid formed with straight lines, but it may be that ofa shape with curves. The movable rocking dogs 28 may be replaced by rotary movable dogs. An embodiment using these modifications is illustrated in FIG. 9.

In reference to FIG. 9, the driving plate 21 is provided with a disk skid 41 freely rotatably mounted thereon, and beside the disk skid 41 there is fixed a dog plate 42. At the tip of the dog plate 42 there is freely rotatably mounted a rotary dog 43 shaped like the cross-wings of a windmill. The center of rotation of the rotary dog 43 is placed at the point where the peripheral surface of the disk skid 41 crosses the'top surface of the fixed skid 11. This fixed skid 11 has the same structure as those shown in FIG. 6.

In this equipment, when the driving plate 21 is progressing, the pieces S are pushed forward by the rotary dogs 43; and when the driving plate 21 is regressing, the

pieces S are raised by the disk skid 41, which rotates' clockwise as the driving plate 21 regresses. Through the rotation of the disk skid 41, the materials S thereon turn over slowly until they are received by the rotary dog 43 right before rolling down onto the fixed skid 11.

When using this apparatus, it may be possible for the pieces S to be turned over by an angle greater than 90C according to the size and shape thereof.

There may be produced scratches on the pieces, be-

cause these slide on the fixed skid; and such scratches may spoil the quality of products.

In order to prevent such trouble, an apparatus shown in FIG. is used, in which the transferrer (such as carrier-chai'ns) 45 for the transference of pieces S is proat the top of the fixed skid 47, andfall down onto the transferrer 45.

The movement of the transferrer 45 is one way; and

the fixed slant skid 47 may be a combination of a disk skid and a rotary dog as the embodiment shown in FIG. 9.

What is claimed is:

l. A method of cooling metal bars heated to a high temperature comprising placing the bars on a cooling bed in groups of bars which are spaced from each other, each group consisting of a plurality of bars with the sides of the bars in each group being in close contact with the adjacent bars in the group, transporting the groups on the cooling bed in a direction transverse to the axes of the bars in intermittent movements while maintaining the spacing between the groups and keeping the bars in the groups in close contact with each other, at the end of each movement turning the bars around their axes while continuing to keep them side by side in the groups in close contact with each other, and subjecting the bars to a cooling medium during such alternate transporting and turning over.

2. A method as claimed in claim 1 wherein said bars are turned over at intervals of from 30 to 60 seconds.

3. A method as claimed in claim 1 wherein the subjecting of the bars to cooling medium comprises cooling the bars by air until the temperature falls to a level below that at which plastic deformation of the bars will occur'due to their own weight, and then applying a cooling medium to the exposed surfaces of the bars for rapidly cooling the surface of the bars to a temperature at which the temperature difference between the sur-' face of the bars and the interior of the bars is insufficient to cause deformation of the bars due to stresses due to cooling, stopping the application of the cooling medium to permit the temperature of the bars to rise until it reaches a temperature close to equilibrium temperature, and alternately repeating the steps of applying the cooling medium and stopping the application of the cooling medium.

4. A method as claimed in claim 3 wherein said cooling medium is water and the step of applying the cooling medium comprises applying jets of water at the rate of 3.5 to l/min.m onto the top surfaces of the bars and at the rate of 20 to 140 l/min.m onto the bottom surfaces of the bars.

5. In a method of cooling metal bars heated to a high temperature in which the bars are placed on a cooling bed in groups of bars which are spaced from each other and each group consists of a plurality of bars with the sides of the bars in close contact with adjacent bars in the group, and the groups of bars are moved along the bed for cooling and are picked up by a crane at the end of the bed, the improvement in which after the bars have been cooled to a temperature below that at which plastic deformation of the bars will occur from handling the bars for rearranging them, the bars are rearranged in groups corresponding to the maximum size of group which can be handled by the crane, and thereafter continuing the cooling while moving the groups of bars along the bed to the position of the crane.

6. An apparatus for cooling metal bars heated to a high temperature, comprising a plurality of spaced parallel fixed skids each having a plurality of fixed dogs freely rotatably mounted thereon at intervals therealong and each tending to rotate to an upright position with a projection on one end thereof projecting above the top of the fixed skids, and stop means on said fixed skids engaging the fixed dogs for preventing rotation thereof in one direction from the upright position, a plurality of driving plates positioned-between the fixed skids and extending parallel thereto and mounted for reciprocal movement in the direction of their length, a plurality of skid means on the upper edges of said driving plates and having the tops thereof projecting above the level of the fixed skids, a plurality of movable dogs freely rotatably mounted on said driving plates at the ends of said skid means toward which bars are to be moved along the skids and each tending to rotate to an upright position with a projection on one end thereof projecting above the top of the fixed skids and stop means on the driving plates engaging the movable dogs for preventing rotation thereof in said one direction from the upright position, and driving means connected to said driving plates for reciprocating said driving plates in the direction of their length.

7. The apparatus as claimed in claim 6 in which each of said skid means is a slant skid having the shape of a trapezoid.

8. The apparatus as claimed in claim 5 wherein the angle of the surface of the slant skid in the direction from which thebars are moved along the skid is from 10 to 20, and the angle of the surface of the slant skid in the direction toward which the bars are moved along the skids is from 40 to the height of the slant skids above the top edge of the driving plates is 0.4 to 1 times the transverse dimension of the bars to be cooled and the length of the top of the slant skid is 0.6 to 1 times the transverse dimension of the bars to be cooled.

9. The apparatus as claimed in claim 6 in which said skid means is a disk freely rotatably mounted on said driving plate, and each of said movable dogs has a cross-shaped element on the end thereof projecting above the driving plate.

10. The apparatus as claimed in claim 6 in which said driving means comprises means for driving said driving plates at a rate of 0.05 to 0.4 meters/sec.

11. In an apparatus for cooling metal bars heated to a high temperature and having a plurality of parallel carrier chains with dogs thereon at intervals therealong for supporting bars transverse to the direction of movement of the chains and a plurality of skids at intervals between said chains and projecting over the top surface of the carrier chains for lifting the bars moved by the sive dogs groups of bars positioned side by side with the movement of the chains and turning the bars over, that sides of the bars in each group being in close contact improvement in which said dogs are spaced from each with adjacent bars in the group.

other sufficiently for accommodating between succes- 

1. A method of cooling metal bars heated to a high temperature comprising placing the bars on a cooling bed in groups of bars which are spaced from each other, each group consisting of a plurality of bars with the sides of the bars in each group being in close contact with the adjacent bars in the group, transporting the groups on the cooling bed in a direction transverse to the axes of the bars in intermittent movements while maintaining the spacing between the groups and keeping the bars in the groups in close contact with each other, at the end of each movement turning the bars around their axes while continuing to keep them side by side in the groups in close contact with each other, and subjecting the bars to a cooling medium during such alternate transporting and turning over.
 2. A method as claimed in claim 1 wherein said bars are turned over at intervals of from 30 to 60 seconds.
 3. A method as claimed in claim 1 wherein the subjecting of the bars to cooling medium comprises cooling the bars by air until the temperature falls to a level below that at which plastic deformation of the bars will occur due to their own weight, and then applying a cooling medium to the exposed surfaces of the bars for rapidly cooling the surface of the bars to a temperature at which the temperature difference between the surface of the bars and the interior of the bars is insufficient to cause deformation of the bars due to stresses due to cooling, stopping the application of the cooling medium to permit the temperature of the bars to rise until it reaches a temperature close to equilibrium temperature, and alternately repeating the steps of applying the cooling medium and stopping the application of the cooling medium.
 4. A method as claimed in claim 3 wherein said cooling medium is water and the step of applying the cooling medium comprises applying jets of water at the rate of 3.5 to 20 1/min.m2 onto the top surfaces of the bars and at the rate of 20 to 140 1/min.m2 onto the bottom surfaces of the bars.
 5. In a method of cooling metal bars heated to a high temperature in which the bars are placed on a cooling bed in groups of bars which are spaced from each other and each group consists of a plurality of bars with the sides of the bars in close contact with adjacent bars in the group, and the groups of bars are moved along the bed for cooling and are picked up by a crane at the end of the bed, the improvement in which after the bars have been cooled to a temperature below that at which plastic deformation of the bars will occur from handling the bars for rearranging them, the bars are rearranged in groups corresponding to the maximum size of group which can be handled by the crane, and thereafter continuing the cooling while moving the groups of bars along the bed to The position of the crane.
 6. An apparatus for cooling metal bars heated to a high temperature, comprising a plurality of spaced parallel fixed skids each having a plurality of fixed dogs freely rotatably mounted thereon at intervals therealong and each tending to rotate to an upright position with a projection on one end thereof projecting above the top of the fixed skids, and stop means on said fixed skids engaging the fixed dogs for preventing rotation thereof in one direction from the upright position, a plurality of driving plates positioned between the fixed skids and extending parallel thereto and mounted for reciprocal movement in the direction of their length, a plurality of skid means on the upper edges of said driving plates and having the tops thereof projecting above the level of the fixed skids, a plurality of movable dogs freely rotatably mounted on said driving plates at the ends of said skid means toward which bars are to be moved along the skids and each tending to rotate to an upright position with a projection on one end thereof projecting above the top of the fixed skids and stop means on the driving plates engaging the movable dogs for preventing rotation thereof in said one direction from the upright position, and driving means connected to said driving plates for reciprocating said driving plates in the direction of their length.
 7. The apparatus as claimed in claim 6 in which each of said skid means is a slant skid having the shape of a trapezoid.
 8. The apparatus as claimed in claim 5 wherein the angle of the surface of the slant skid in the direction from which the bars are moved along the skid is from 10 to 20, and the angle of the surface of the slant skid in the direction toward which the bars are moved along the skids is from 40* to 50*, the height of the slant skids above the top edge of the driving plates is 0.4 to 1 times the transverse dimension of the bars to be cooled and the length of the top of the slant skid is 0.6 to 1 times the transverse dimension of the bars to be cooled.
 9. The apparatus as claimed in claim 6 in which said skid means is a disk freely rotatably mounted on said driving plate, and each of said movable dogs has a cross-shaped element on the end thereof projecting above the driving plate.
 10. The apparatus as claimed in claim 6 in which said driving means comprises means for driving said driving plates at a rate of 0.05 to 0.4 meters/sec.
 11. In an apparatus for cooling metal bars heated to a high temperature and having a plurality of parallel carrier chains with dogs thereon at intervals therealong for supporting bars transverse to the direction of movement of the chains and a plurality of skids at intervals between said chains and projecting over the top surface of the carrier chains for lifting the bars moved by the movement of the chains and turning the bars over, that improvement in which said dogs are spaced from each other sufficiently for accommodating between successive dogs groups of bars positioned side by side with the sides of the bars in each group being in close contact with adjacent bars in the group. 